Synthesis and characterization of ZnAI2O4 precursor in relation to different basic media

Central Glass and Ceramic Research Institute, Kolkata-700 032, India Department of Chemistry, Jadavpur University, Kolkata-700 032, India Ceramic Engineering Division, Department of Chemical Technology, University of Calcutta, 92, A. P. C. Road, Kolkata-700 009, India E-mail: tapanparya@yahoo.co.in Fax: 91-33-23519755 Manuscript received 18 July 2003, revised 6 January 2004, accepted 19 March 2004 The role of different basic media for the preparation of Zn-Al based hydroxy compounds, leading to the formation of ZnAI2O4 spinel at low temperature was investigated. Nitrate salts of respective cations with molar ratio for ZnO : Al2O3 as 1 : 1 were used for coprecipitation. DTA, TGA, XRD, IR spectroscopy and SEM technique were utilised for characterization of the precursor hydroxy compounds as well as the final products obtained by heat treatment of the hydroxy compounds at different temperatures. It had been found that spinel formation was very much influenced by the nature of mixed hydroxide precursors obtained by using different basic media. The thermal treatment of the coprecipitated gel powders led to the formation of ZnAI2O4 at relatively low temperature (500°). Mixed hydroxide gel powder obtained by using NH4OH-hexamethylene tetramine (HMT) as basic medium was observed to exhibit best results so far as spinel formation at low temperature was concerned